Pharmacogenetics: Dose-response curves for atropine administration will be obtained on three inbred strains of rabbits (As/As, AS/as, and as/as) that differ with respect to inheritance of a genetically determined circulating enzyme, atropine esterase. Effects of genetic input will be quantified with respect to the drug's action on heart rate, blood pressure and renal blood flow. Active transport of a series of anionic phenolsulfonphthaleins will be studied in vitro on needle biopsy samples of various mammalian kidneys as a device to identify proximal convoluted segments. This in turn may help to localize glomeruli. Application of this procedure could enable clinical nephrologists quickly to separate tissue fragments of limited size into several samples, each containing glomeruli needed for various routine microscopic diagnostic procedures. Intracellular osmoregulation by erythrocytes and muscle cells of certain marine elasmobranchs will be studied with particular emphasis on the kinetic role amino acids play in accommodating cells to dilution of their extracellular fluid environment.